The major project in our laboratory is to determine pathogenetic mechanisms involved in the induction of plasmacytomas by the intraperitoneal introduction of various substances (e.g., paraffin oils, solid plastic discs). We have recently found a new potent plasmacytomagenic agent dimethylpolysiloxane, the principle component of the gels used in breast implants. This material in relatively small amounts induces the formation of a granulomatous tissue on mesenteric surfaces. Our major focus has been on defining genes that determine susceptibility and resistance to plasmacytoma induction. We have found two resistance genes on Chromosome 4. These genes appear to be relatively late acting and inhibit the progression of foci to plasmacytoma. We continue to refine our focus assay system for the earlier detection of susceptibility and resistance. This work has been delayed because of the apparent development of a mutation in our BALB/cAnPt colony that partially confers resistance to plasmacytoma induction. In collaboration with Siegfried Janz a PCR amplification system has been developed for the detecting of IgSa-C-myc illegitimate recombinations that occur in the chromosomal translocation T(12;15) which is found in 90% of mouse plasmacytomas induced by paraffin oils. We are currently evaluating whether the frequency of these translocations is favored in plasmacytoma susceptible strains.